Interpretive Summary: Throughout eastern North America, the dogwood borer has become a serious wood-boring pest of apple planted on dwarfing or size-controlling rootstocks due to their tendency to produce burr knot tissue, a favored oviposition site for female dogwood borer. Based on an intense monthly sampling regime in two newly planted apple orchards in West Virginia and Virginia, we found that rootstock, tree variety, and cultural management practices were strongly related to the presence and extent of the infestaion. We utilized geospatial statistics to characterize how dogwood borer infestation spread throughout these particular orchards and found moderate to high degrees of aggregation in infestation on neighboring trees, within independent infestation sites at distances greater than or equal to 7.5 m. These results will be useful in developing a sampling plan for determining the need for insecticide applications against dogwood borer.

Technical Abstract:
The temporal and spatial patterns of infestation by larval dogwood borer, Synanthedon scitula (Harris), was studied during 2002–2004 in two newly planted apple orchards in West Virginia and Virginia. The orchards contained several rootstock-variety combinations grown under different cultural management regimes. Data on larval infestation collected over the entire sampling period and across years showed that rootstock, tree variety, and cultural management practice were significantly associated with the presence and extent of dogwood borer infestation. In West Virginia, dogwood borer infestation was significantly greater on trees planted on M.26 rootstock compared with M.7 rootstock and on trees fitted with spiral wrap tree guards compared with trees with bare trunk and soil mound treatments. In Virginia, the proportion of infested trees was significantly greater for Idared tree varieties compared with Buckeye Gala and on trees fitted with spiral wrap tree guards compared with other trunk treatments. The results of geostatistical analysis indicated that there were high to moderate degrees of aggregation in dogwood borer infestations on neighboring apple trees with ranges of spatial autocorrelation from 7.50–19.87 m. The spatial patterns of the aggregation of infestation in the West Virginia and Virginia orchards were best described by the spherical and exponential semiovariogram models, respectively. Interpolated surface maps of infestation revealed local hot spots, which were generally more prevalent within tree guard treatments, and were typically found where dogwood borer infestations originated. Results are discussed in relation to the development of sampling plans for management of dogwood borer larvae and for site-specific agriculture.